Large commercial aircraft comprise a variety of different systems that are designed with a certain redundancy depending on the functions they have to provide. The provision of a continuous electrical power supply, for example, is elementary for a correct function of the aircraft, such that often a high reliability through a combination of a plurality of different power supply systems is achieved. Besides engine driven generators an aircraft usually comprises a ram air turbine for emergency cases that either provides hydraulic power for driving a generator by means of a hydraulic motor or for driving the generator directly. A ram air turbine is extendable into the air flow in the case of an emergency but has limited power in low velocity flight situations, e.g. during the approach.
Alternative concepts for providing emergency power in aircraft exist by means of fuel cell systems that consume oxygen and hydrogen from dedicated tanks. DE 10 2005 010 399 B4 discloses an aircraft with a fuel cell system, which is independent from ambient air and which is switched off during normal flight.
It is furthermore known to use the exhaust gas of a fuel cell for inerting a space in a vehicle and for suppressing fire. For example, DE 10 2005 053 694 discloses a fuel cell system for extinguishing fires in an aircraft, wherein the fuel cell is supplied with hydrogen and air and is used for generating nitrogen enriched air.
Lastly, DE 10 2004 058 430 discloses a multi functional fuel cell system with an increased safety of operation.